The present invention relates in general to an infiltration cannula permitting the infiltration of very large volumes of tumescent fluid in a safe and painless manner.
Definitions:
infiltration: an injection that causes a fluid to permeate or percolate through pores or interstices. Thus an infiltration refers to an injection directly into tissue.
infusion: an injection that pours a fluid into a place or into (the lumen of a blood) vessel. Thus an infusion refers to an intravascular injection.
injection: The action of forcing a fluid, etc. into tissue or cavity, as by means of a syringe, or by some impulsive force.
Tumescent Technique, Tumescent Infiltration: The tumescent technique is a method of subcutaneous drug delivery of large volumes of very dilute medication together with dilute epinephrine in isotonic solution of crystalloid (e.g. physiologic saline, lactated Ringer's solution, Hartman's solution, etc) infiltrated directly into subcutaneous fat or muscle or along the exterior length of a vein to produce swelling and firmness, or tumescence, of the targeted tissues, and thus produce very slow systemic absorption as a result of intense subcutaneous vasoconstriction, as well as direct hydrostatic compression of capillaries and veins.
Tumescent Drug Delivery, Tumescent Delivery: Tumescent drug delivery and synonyms refer to the tumescent technique for delivering a drug into the subcutaneous space. In other words, tumescent delivery is a process of infiltration of very large volumes of very dilute solutions of therapeutic substances dissolved in a crystalloid solution into subcutaneous tissue to the point of producing tumescence of the targeted tissue. Drugs other than lidocaine can be administered by means of tumescent delivery, that is, by subcutaneous infiltration of extremely dilute drug, with or without a vasoconstrictor such as epinephrine.
Tumescent Local Anesthesia (TLA) is local anesthesia produced by direct infiltration into subcutaneous tissue of large volumes of very dilute lidocaine (e.g., less than or equal to 1 gram/liter) and epinephrine (e.g., less than or equal to 1 milligram/liter) with sodium bicarbonate (e.g., 10 milliequivalents/liter) in a crystaloid solution such as physiologic saline (NaCl) or lactated Ringer's solution. Although higher concentrations can be used and still qualify as TLA, it is generally safer to use the least (lowest) effective concentration.
Tumescent Local Anesthetic Solution (TLA Solution) is the local anesthetic solution used to produce TLA. Typically, a TLA Solution consists of a 10 to 20 fold dilution of commercially available concentration of lidocaine and epinephrine. Thus, a commercial solution of lidocaine and epinephrine contains 10 grams of lidocaine per liter (10 gm/L) and 10 milligrams of epinephrine per liter. In contrast TLA Solution typically contains very dilute lidocaine (≦1 gram/liter) and epinephrine (≦1 milligram/liter) with sodium bicarbonate (10 milliequivalents/liter) in a crystalloid solution such as physiologic saline or lactated Ringer's solution. Typically the volume of infiltrated TLA Solution is so large that the skin and subcutaneous tissue becomes tumescent, in other words swollen and firm.
tumescent, tumescence: swollen and firm
tumescent liposuction: liposuction performed totally by local anesthesia using tumescent local anesthesia.
tumescent fluid, tumescent solution: dilute solutions of therapeutic substances dissolved in a crystalloid solution intended for tumescent delivery into subcutaneous tissue.
tumescent “drug”: the “drug” in the context as an ingredient in a tumescent solution and its pharmacokinetic behavior as a result of the pharmacokinetics of a tumescent solution; for example tumescent lidocaine, tumescent epinephrine, tumescent antibiotic.
Tumescent Pharmacokinetics: The absorption pharmacokinetics (the pharmacologic and physiologic factors associated with the systemic absorption of a drug) after tumescent infiltration of a drug is dramatically slower than the rate of systemic absorption of routine injection of the drug. The intense vasoconstriction induced by epinephrine, slows the rate of drug absorption into the central circulation and prolongs the local effects of the drug. For example, the duration of routine local anesthesia with lidocaine is typically 2 hours, in contrast the duration of local anesthesia with tumescent local anesthesia may be 12 to 18 hours or more. A similar prolonged effect of tumescent antibiotic infiltration significantly improves the prophylactic effect of preoperative antibiotic therapy in the prevention of surgical site infections.
adit: a small round hole in the skin (typically 1 mm, 1.5 mm or 2 mm diameter) made by a skin-biopsy punch, and intended to be an access port for percutaneous entry into the subcutaneous fat by a tumescent infiltration cannula and/or a liposuction cannula.
Many medical procedures require infiltration of fluids, such as a local anesthetic. For example, liposuction may be performed entirely by tumescent local anesthesia which was invented by Jeffrey A. Klein. Dr. Klein first published the description of tumescent local anesthesia to perform liposuction in 1987 (Klein J A. The tumescent technique for liposuction surgery. J Am Acad Cosmetic Surg 4:263-267, 1987). The tumescent technique was invented in order to eliminate the dangers of liposuction surgery under general anesthesia and the associated excessive bleeding. With proper technique, tumescent infiltration permits liposuction totally by local anesthesia with virtually no surgical blood loss.
One method of infiltration of local anesthetic is via a blunt tipped infiltration cannula. Infiltrators are known as sprinkler-tip or Klein™ (the present applicant) needle infiltrators. These cannulas are constructed out of a rigid stainless steel and have one or more apertures, which are typically round or oval, and are distributed about the distal end of the cannula. The apertures are distributed over about 15% to 25% or less than 5.0 cm. of the distal end of the cannula needle. These traditional infiltration cannulas are intended to be inserted through a small incision in the patient's skin and then moved in and out through the subcutaneous tissue while a dilute solution of local anesthetic (or other pharmaceutical solution) is ejected through the distal apertures. Since the cannula needle is moved in and out, only the distal end (e.g., about 15% to 25%) of the cannula needle may have apertures. Otherwise, fluid may squirt out of the apertures and onto medical professionals when the cannula needle is moved out too much. Such infiltrators typically have a blunt tip and require the placement of a small hole (made by a one mm skin-biopsy punch or a small surgical blade) through which the blunt tipped cannula can be passed. Unfortunately, the piston-like in and out motion of the cannula causes the patient discomfort.
Another type of infiltration cannula is the sharp tipped tumescent infiltration cannula which is available as 1) a single long sharp needle similar to a spinal needle and 2) a group of short sharp hypodermic needles each connected by separate plastic tube to a manifold that distributes TLA solution. The first type of needle is inserted into subcutaneous fat and infiltration proceeds while the needle is continuously moved in and out along paths that radiate from the skin puncture site. A targeted area is eventually anesthetized after multiple skin punctures. The second type, the group of short sharp needles, consists of a group of individual hypodermic needles each attached to an individual IV extension tube, which are in turn connected to a multi port manifold which connected to a reservoir (IV bag) of tumescent fluid. These sharp-tipped tumescent infiltration devices have been associated with puncture-injury to deeper tissues such as the lungs causing pneumothorax or intra-abdominal viscera causing peritonitis.
In summary, there are two causes of pain associated with the blunt and sharp tipped infiltration cannulas. One significant cause of pain is a continuous in and out motion of the cannula as it moves through non-anesthetized tissue. In order to deliver tumescent anesthetic solution throughout an entire compartment of subcutaneous fat, the anesthetist must move the cannula with a continuous to and fro reciprocating motion, and repeatedly change directions. Each advance of the cannula through fat causes discomfort and pain. The second cause of pain is associated with an excessively rapid distention of tissue resulting from a high rate of fluid injection into a relatively small volume of tissue via limited number of holes on the distal tip of the infiltration cannula. Ironically, the pain associated with each of these two factors often necessitates the use of narcotic analgesia, IV sedation, or general anesthesia in order to infiltrate local anesthesia. The present invention eliminates or greatly reduces these two sources of pain.
Another method of fluid insertion is via a peripherally inserted central catheter, also called a PICC line comprising an elongate plastic tube that is placed inside a vein of the patient. PICC lines are typically used for procedures requiring delivery of fluids over a prolonged period of time. For example, a PICC line may be used when a patient needs to receive intravenous (IV) fluids, such as medication or nutrients over a prolonged period of time, such as a week or more.
The On-Q® Pain Management System marketed by I-Flow® Corporation employs a flexible plastic or silicone catheter system for continuously providing local anesthetic. This system provides prolonged local anesthesia by means of an elastomeric (elastic container) device that continuously infiltrates a solution of local anesthesia over many hours. The On-Q® device comprises a long soft flexible tube with many small holes arranged along a significant portion of the tube. The On-Q® device is designed to be initially positioned within a surgical wound at the time of surgery. After the surgical wound is closed, the On-Q® device permits slow steady infiltration of a local anesthetic solution into the wound, thereby attenuating post-operative pain. The On-Q® device cannot be inserted through a tiny hole in the skin into subcutaneous tissue. Therefore the On-Q device cannot achieve infiltration of local anesthesia and prevent post-operative pain in a preemptive fashion. It has been shown that preemptive local anesthesia in the form of peripheral nerve blocks, can prevent nocioception by the central nervous system (CNS) during general anesthesia, and thereby prevent chronic post-operative pain syndromes similar to “phantom-limb syndrome.” Thus there is a need for a simple device that can permit the direct percutaneous insertion of a multi-holed infiltration cannula into subcutaneous tissue for the localized delivery of medications such as local anesthetics, chemotherapeutic agents, or crystalloids for parenteral hydration.
Traditional techniques for subcutaneous injection of local anesthetic solutions (e.g. peripheral nerve blocks) use a high-concentration/low-volume of local anesthetic. This is associated with a rapid systemic absorption of the local anesthetic. In order to achieve a prolonged local anesthetic effect, the traditional techniques for using local anesthetics necessitate either frequent repeated injections or slow continuous subcutaneous infusion of the local anesthetic. As described above, repeated injections or piston-like movement of the cannula causes patient discomfort. Slow continuous infiltration may not be desirable in certain situations. Furthermore, continuous infiltrations restrict patient movement for extended periods of time which also cause the patient discomfort. Thus, there is a need for a system for infiltration of a local anesthetic into intact subcutaneous tissue (not necessarily into peri-incisional tissue) which decreases patient discomfort pre-emptively, and allows prolonged local anesthesia either by rapid (less than 10 to 15 minutes) bolus injections, extended infiltration (e.g. over intervals ranging from 15 minutes to several hours) or continuous slow infiltration over many hours to days. Furthermore there is a need for a devise that can provide pre-emptive local anesthesia before a surgical wound is created. There is also a need for a percutaneously-insertable infiltration cannula, with applications that are unrelated to the delivery of local anesthesia, which can be easily inserted by rescuers with minimal clinical skill or training. One example is the need for a cannula that permits emergency fluid resuscitation in situations where an IV cannot be established such as nighttime military combat conditions where using a flash light to establish an IV access would be extremely dangerous. Another example is the need to provide emergency fluid resuscitation to large numbers of patients in acute epidemic diarrhea (dehydration) associated with biological warfare, or mass-trauma situations such as a natural disaster (earth quake) or terrorist attack. There is also a need for a device that can easily provide localized fluid resuscitation to burn victims whereby fluid is infiltrated into the subcutaneous tissue directly subjacent to burned skin.
Other types of devices for delivering fluid to a patient exist in the prior art. For example, U.S. Pat. Pub. No. 2003/0009132 (Schwartz et al.) is directed to a micro-intravascular (never extra-vascular) catheter for infusing milliliter quantities of drugs for the lysis of intravascular blood clots (i.e., a micro target). Another embodiment of the Schwartz device is intended to improve the precision and safety of intra-myocardial delivery of micro-liter volumes of fluid for biologic gene therapy based angiogenesis.
Unfortunately, the Schwartz device requires a sterile high tech hospital environment and demands fluoroscopy and ultrasound guidance. The Schwartz device requires a highly trained, experienced and skilled medical professional to operate. In particular, the Schwartz infiltration catheter is defined by its obligatory guidewire and intravascular target. The intravascular insertion of the catheter via the guidewire is a complex procedure that requires significant clinical training, experience and skill. Specifically, it involves 1) preparation with a sterile surgical field, 2) making a skin incision and inserting an introducing catheter having coaxial stylet into the targeted vessel, 3) removing the stylet, 4) inserting the guidewire through the introducing catheter and into the vessel, 5) withdrawing the introducing catheter from the vessel without disturbing the intravascular location of the guidewire, 6) slipping the distal tip of the infiltration catheter over the proximal end of the guidewire, and advancing the infiltration catheter over the considerable length of the guidewire through the skin and into the intraluminal space of the targeted vessel, 7) withdrawing the guidewire and attaching the proximal end of the infiltration catheter to a source of the therapeutic fluid to be delivered into the targeted vessel. This insertion procedure is so specialized that a majority of physicians do not have the requisite expertise to qualify for hospital privileges for inserting an intravascular catheter using a guidewire. Locating a clotted blood vessel and inserting the Schwartz catheter into the vessel requires the ultrasound guidance.
As understood, an important feature of the Schwartz device is the shape, size, direction and pattern of the holes on the infiltration cannula. As stated in paragraph 15 of the Schwartz disclosure, “there is a need for an injection device that gives control over the concentration, pattern, and location of the deposition of an injectate.” The Schwartz device is intended to improve directional control over the direction of injection of minute volumes of injectate.
The Schwartz device appears to be specifically designed to avoid vascular compression. For the small needle embodiment of Schwartz, vascular compression resulting from injecting excessive volume of drug into myocardium may precipitate infarction or arrhythmia. Likewise, for the long cannula embodiment of Schwartz vascular compression appears to be contraindicated. The goal of infusing fluid into a vessel containing a blood clot is to open the vessel, and not compress it.
The Schwartz device also appears to be incapable of large volume (e.g., multi liter) subcutaneous infiltration. The long plastic Schwartz catheter appear to be specifically intended for intravascular use. Moreover, Schwartz cannula cannot have holes distributed along 100% of its entire length based on a contention that such situation will lead to a contradictory situation. If the Schwartz device does have holes along its entire length then either the entire length of the cannula would have to be positioned inside a vessel (unlikely without attaching the cannula proximally to another catheter in which case the bulky attachment mechanism would have to be passed through the wall of the vessel) or else some of the holes would have an extravascular location (unlikely because the therapeutic fluid would either leak onto the patient's skin or extravasate into the perivascular and subcutaneous tissues). In either case, the potential for serious adverse effects would be significant.
Moreover, the Schwartz device does not appear to be capable of being reciprocated in and out of the subcutaneous tissue of the patient to locally anesthetize an entire compartment.
In summary, the Schwartz infiltrator is intended for 1) intravascular insertion which demands a complex guidewire procedure involving several steps, 2) intravascular drug delivery (for lysis of blood clots) or intra myocardial injections, 3) injection of a miniscule volume (micro liters) of drug.
Another type of device for delivering fluid to a patient is described in U.S. Pat. No. 6,524,300, issued to Meglin. Similar to the Schwartz device, the Meglin device appears to be an intravascular device intended to inject a “medical agent into the target lumen of the body.” (see Col. 2, lns. 41-48). Meglin is specifically intended to be inserted intralumenally into “a lumen of a blood vessel or another cavity within a patient's body.” (see Col. 1, lns. 14-19). This is precisely opposite the goal of a tumescent infiltration cannula. A tumescent infiltration cannula is intended to deliver drugs to the subcutaneous space which excludes the vascular space and cavitary space. As such, the Meglin device appears to be specifically designed to avoid vascular compression and to not induce vasoconstriction. An important aspect of the Meglin device appears to be the size and density of the apertures to control the rate of flow of fluidic medication. Moreover, it appears that the medical professional utilizing the Meglin device requires a great deal of training, expertise and education based on a contention that the infusion segment of the device is located intravascularly by locating a radiopaque marker band with a fluoroscopy.
Another type of device for delivering fluid to a patient is described in U.S. Pat. No. 6,375,648, issued to Edelman, et al. Similar to prior art blunt or sharp tipped infiltration cannulas, the apertures are restricted to the distal 25% of the cannula. The reason is that otherwise, the fluidic medication would squirt out of the apertures and contaminate the operating room. Col. 2, lns. 22-25 states that “once within the tissue of a patient a treatment solution may be infused into the tissue by working the cannula 20 through the fat tissue of the patient.” As understood, the Edelman device suffers from the same deficiencies discussed above in relation to the blunt or sharp tipped infiltration cannulas. The Edelman cannula is reciprocated in and out of the subcutaneous tissue, and thus, causes pain or discomfort to the patient. Moreover, the only novel aspect of Edelman appears to be the cannula's Teflon coating.
Surgical site infections are a significant source of post-operative morbidity and mortality. They account for 17% of all hospital acquired infections, require prolonged hospital stays and contribute substantially to health care costs. The incidence of surgical site infection is a function of the type of surgical procedure, the surgeon, and the hospital. The risk of SSI is significantly associated with a number of factors including anesthetic risk scores, wound class and duration of surgery.
The true incidence of SSI is probably higher than what has been reported in the literature. The primary surgical team is often not aware of incisional infections diagnosed after hospital discharge. Patients who had SSI diagnosed after discharge require substantially more outpatient visits, emergency visits, radiology services and home healthcare services. A study published in 2004 found such infections cost $6,200 per patient for home care expenses associated with wound care. The major sources of infection are microorganisms on the patient's skin. A number of preoperative skin care techniques have been used to limit concentrations of bacteria at the surgical site, including antiseptic preparations, adhesive barrier drapes, topical antibiotics, hair removal and hand hygiene.
Antimicrobial prophylaxis with intravenous (IV) antibiotics is currently the most important clinical modality for preventing SSI. The consensus recommendation for antimicrobial prophylaxis is for antimicrobial agents to be given as an IV infusion of antibiotics to be given within the first 60 minutes before surgical incision and that prophylactic antimicrobial agents be discontinued within 24 hours of the end of surgery.
Recent Center for Disease Control (CDC) guidelines for antimicrobial prophylaxis do not mention preoperative perilesional infiltration of antibiotics (http://www.cdc.gov/ncidod/dhqp/pdf/guidelines/SSI.pdf). A recent review of surgical site infections only discussed intravenous (IV) delivery of prophylactic antibiotics. The possibility of preoperative peri-incisional infiltration to prevent SSI was not considered.
Several studies of SSI in the 1980's compared the effectiveness of antimicrobial prophylaxis by IV infusion or by peri-incisional infiltration. A 1981 study of the incidence of wound infection among 405 abdominal surgery patients found no significant difference between 1 gm of cephaloridine given intravenously or intra incisional at the end of the surgery. Following this trial, IV antibiotics at the induction of anesthesia became standard practice.
An IV infusion of fluid is a common medical procedure to treat patients. Unfortunately, an IV infusion is associated with an inherent expense, difficulty and risk. There are also unfortunately times when an IV line cannot be established in the patient. By way of example and not limitation, the patient may be burned such that a vein of the patient cannot be located to establish an IV access. The patient may have been traumatized in such a way that will not allow a doctor to perform an IV cut down procedure. Additionally, the patient may be very obese such that the vein of the patient is difficult to locate. In other situations, occurring in remote locations where a trained medical professional is not available to establish the IV such as the international space station or on an airplane. Currently, there does not appear to be any in flight capability for treating an acute traumatic injury on a plane or on the space shuttle. If the pilot or astronaut survives the immediate effects of an explosion, burn, or decompression injury, or if there is an acute non-traumatic medical illness, it is assumed that the victim must return to terra firma for any significant therapeutic intervention such as providing systemic fluid replacement. Other situations include a mass casualty situation where there are insufficient number of trained medical professionals compared to the number of victims/patients, etc.
Other methods of delivering a drug to a patient other than an IV infusion may be oral delivery of the drug. Unfortunately, oral delivery of the drug results in inconsistent absorption of the drug into the gastrointestinal tract. The drug may alternatively be delivered via periodic intramuscular injections. Unfortunately, the fluidic drug serum may have varying levels of concentration at each of the periodic injections.